Several assembly processes for manufacturing electronic systems are widespread in the art for large-scale production. Basically, each assembly process provides for mounting one or more electronic devices onto an electronic board (e.g., a Printed Circuit Board or PCB). Generally, each electronic device comprises a chip (or more) of semiconductor material on which an actual electronic component is integrated. The chip is enclosed in a package of insulating material in order to be insulated and protected from the outside environment. The package exposes conducting pins, which are coupled with corresponding terminals of the conducting chip. The pins are soldered to conducting tracks formed on the electronic board. This allows the interaction between the electronic component, comprised in the electronic device, and other electronic devices mounted on the electronic board in a similar way, through the conducting tracks properly connected to one another.
The soldering between the pins of the electronic devices and the tracks of the electronic board should be performed homogeneously for ensuring proper operation and/or performance of the electronic system. At the same time, the soldering should ensure a stable mechanical connection between the electronic devices and the electronic board.
For example, a known soldering technique is the wave soldering technique. In this case, the electronic devices are initially glued onto the electronic board by means of an adhesive paste, at conducting traces being precursor of the tracks of the electronic board. Subsequently, the assembly thus obtained is placed over a bath of molten solder paste, with a gluing surface of the electronic board (on which the electronic devices are glued) facing downward. The assembly is then flooded with a wave of molten solder paste, which laps the electronic board in such a way to bind to the conducting traces of the electronic board and to the pins of the electronic devices. In this way, the corresponding conducting tracks that create an electrical and mechanical coupling between the electronic devices and the electronic board are formed.
The wave soldering technique described above, however, may be troublesome with certain types of electronic devices. For example, this may occur in the case of Surface Mounting Technology or SMT electronic devices having pins substantially exposed on a mounting surface of the electronic device on the electronic board—known in the art as “No-Lead” or “Micro-lead”—especially if of small size.
In fact, a gap between the pins and the conducting traces may be too narrow for allowing the wave of solder paste to enter it in an optimal way—in particular, in the case of pins with a relatively large area. Furthermore, the electronic devices may be positioned with the mounting surface being not perfectly parallel to the electronic board due to a reduced number and/or a sub-optimal distribution of sites for dispensing the most common adhesive pastes on the mounting surface of the electronic devices. Indeed, the miniaturization of the electronic device accordingly reduces its mounting surface, while the size of the pins remains substantially unchanged for ensuring the same current density, thereby reducing the available space on the mounting surface for the gluing sites—for example, no longer available in some perimeter locations thereof. Therefore, due to such an imperfect positioning of the electronic devices on the electronic board, during the wave soldering the solder paste may be distributed unevenly. For these reasons it may occur that the coupling between the pins and the conducting tracks may be not formed in a satisfactory manner or may not be formed at all. The electronic system thus assembled would have reduced performance and working life, down to be completely unable to operate.